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Date:   Mon, 25 Sep 2023 09:09:51 +0200
From:   Michal Hocko <mhocko@suse.com>
To:     Kees Cook <keescook@chromium.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Shakeel Butt <shakeelb@google.com>,
        Roman Gushchin <roman.gushchin@linux.dev>,
        Johannes Weiner <hannes@cmpxchg.org>,
        "Matthew Wilcox (Oracle)" <willy@infradead.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Tom Rix <trix@redhat.com>, Yosry Ahmed <yosryahmed@google.com>,
        Yu Zhao <yuzhao@google.com>, Miaohe Lin <linmiaohe@huawei.com>,
        Yafang Shao <laoar.shao@gmail.com>,
        Kefeng Wang <wangkefeng.wang@huawei.com>,
        Qi Zheng <zhengqi.arch@bytedance.com>,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
        linux-hardening@vger.kernel.org
Subject: Re: [PATCH] mm/memcg: Annotate struct mem_cgroup_threshold_ary with
 __counted_by
Message-ID: <ZREyPxSXgjmikITj@dhcp22.suse.cz>
References: <20230922175327.work.985-kees@kernel.org>
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On Fri 22-09-23 10:53:28, Kees Cook wrote:
> Prepare for the coming implementation by GCC and Clang of the __counted_by
> attribute. Flexible array members annotated with __counted_by can have
> their accesses bounds-checked at run-time checking via CONFIG_UBSAN_BOUNDS
> (for array indexing) and CONFIG_FORTIFY_SOURCE (for strcpy/memcpy-family
> functions).
> 
> As found with Coccinelle[1], add __counted_by for struct mem_cgroup_threshold_ary.
> 
> [1] https://github.com/kees/kernel-tools/blob/trunk/coccinelle/examples/counted_by.cocci
> 
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Shakeel Butt <shakeelb@google.com>
> Cc: Roman Gushchin <roman.gushchin@linux.dev>
> Cc: Johannes Weiner <hannes@cmpxchg.org>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
> Signed-off-by: Kees Cook <keescook@chromium.org>

Acked-by: Michal Hocko <mhocko@suse.com>

> ---
>  include/linux/memcontrol.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 45d0c10e86cc..e0cfab58ab71 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -143,7 +143,7 @@ struct mem_cgroup_threshold_ary {
>  	/* Size of entries[] */
>  	unsigned int size;
>  	/* Array of thresholds */
> -	struct mem_cgroup_threshold entries[];
> +	struct mem_cgroup_threshold entries[] __counted_by(size);
>  };
>  
>  struct mem_cgroup_thresholds {
> -- 
> 2.34.1

-- 
Michal Hocko
SUSE Labs